3.2.4 Immune System

Pathogens

Microorganisms that cause disease.

Bacteria

A type of pathogen that can cause disease.

Fungi

A type of pathogen that can cause disease.

Viruses

A type of pathogen that can cause disease.

Antigens

Specific molecules on the surface of cells used in cell recognition.

Immune Response

The reaction of the immune system to antigens, involving the identification of foreign substances.

Non-Specific Immune System

The part of the immune system that is effective against a wide range of pathogens from birth.

Specific Immune System

The part of the immune system that is slow and effective against specific pathogens, with a faster response upon re-infection.

Physical Barriers

Non-specific defenses that protect the body, such as skin and mucous membranes.

Phagocytosis

The process by which phagocytes engulf and digest foreign substances.

Phagocyte

A type of immune cell that engulfs pathogens.

Antigen-Presenting Cell

A phagocyte that displays antigens from pathogens on its cell membrane.

T Lymphocytes

Immune cells that carry out the cellular response by recognizing non-self-antigens.

Cytotoxic Cells

A type of T cell that destroys infected body cells.

Memory T Cells

T cells that enable a rapid response to future infections by the same pathogen.

Helper T Cells

T cells that stimulate other immune cells through chemical signals.

Endocytosis

The process by which a cell engulfs a substance to bring it into the cell.

Lysosome

An organelle that contains enzymes to digest pathogens.

Phagosome

A vesicle that contains the engulfed pathogen within a phagocyte.

Hydrolyse

The process of breaking down substances using water, often performed by lysosomes.